An internal combustion engine in a vehicle typically is in fluid communication with an air induction system and an air exhaust system for providing air to the engine, and exhausting air from the engine, respectively. In the internal combustion engine, sound energy is often generated in the form of acoustic pressure waves as air flows through the air induction and exhaust systems. In particular, vibrations are often caused by intake air flowing through an air feed conduit of the air induction system. Specifically, vibrations are caused by the induction of air into a cylinder of the internal combustion engine by a cyclic movement of a piston slidably disposed in the cylinder.
Oftentimes in vehicles, such as luxury vehicles, for example, sound energy generation by the air induction is desirably minimized. Resonators have been employed to reduce engine intake noise and improve noise comfort in the vehicle interior. Resonators operate by reflecting sound waves generated by the engine 180 degrees out of phase. The combination of the sound waves generated by the engine with the out of phase sound waves results in a reduction or cancellation of the amplitude of the sound waves. Such resonators typically include a single, fixed volume chamber for dissipating the intake noise. Multiple resonators are also frequently used to attenuate several sound waves of different frequencies.
Many vehicles also use interior sound quality to differentiate from competition. For example, in high performance vehicles and sports cars, the transmission of sound energy to the vehicle interior may provide for a more aesthetically intensive driving experience. The air induction system of a turbo-charged engine, however, is known to generate less sound energy than the induction system of a normally-aspirated engine. Additionally, the air induction system in many vehicles is disposed in a location that does not permit a desired amount of sound to reach the vehicle interior. Thus, devices have been employed to transmit sound energy generated by high pressure areas in the induction system to the engine compartment or the vehicle interior. The sound quality in the vehicle interior may thereby be modulated to provide an aesthetically desirable sound quality.
A known device for generating sound in vehicles has included, for example, a hollow body separated into at least two chambers by a sound transmitting device. The device has sometimes included an output conduit section for transmission of sound to the vehicle interior. Sound generation devices of the art also have employed a spring mass system, such as an oscillating bellows, that typically has a single resonant frequency.
A device for the targeted transmission of sound from an induction tract of an internal combustion engine into the interior of the motor vehicle is disclosed in U.S. Pat. No. 6,600,408. The device includes a hollow transmission body that communicates with the induction tract on the intake side and emits sound on the output side of the vehicle interior. U.S. Pat. No. 6,644,436 discloses a device for noise configuration in a motor vehicle that has a hollow body which is divided into at least two spaces. Further, U.S. Pat. No. 6,848,410 discloses a device for targeted sound transmission from an intake tract that has several resonator chambers operating in parallel.
There is a continuing need for a sound generator that may be used to selectively modulate sound quality in the engine compartment or the vehicle interior. Desirably, the sound generator is readily configurable to meet various tuning requirements. It is also desirable that a structural complexity of the sound generator is minimized.